Besides the use for conventional foodstuff purposes, the botanical or chemical components of crop raw material have been isolated to be used for industrial purposes. The most extensive industrial implementations are starch separating processes using corn, wheat and barley as a raw material. The main by-products of these processes are gluten, which is recoverable from corn and wheat, other protein fractions, corn oil, and wheat germ oil, as well as fractions mainly used as feed. The methods conventionally used for separating starch from crop raw material can be classed into wet milling methods or combinations of dry process steps and wet milling.
In grain fractioning, various mechanical methods are used, such as screening, air classification, sedimentation as well as extracting and dissolving processes. For oat grinding, milling devices generally suitable for the grinding of other crops have been applied. The U.S. Pat. No. 4,220,287 discloses a roll milling device equipped with either smooth or fluted rolls.
For oat fractioning, prior known methods in most cases relate to separating an individual component from the oat grains. The protein separation of oats has been an object for the most extensive study, the central method having been dissolving protein into basic solutions and precipitating by means of acids at the isoelectric point.
In several described processes, the alcalic extraction is preceded by a solvent extraction by means of hydrocarbon, halogenated hydrocarbon, aliphatic alcohols, or acetone, in order to remove the crude oil, aiming at facilitating the subsequent separating steps and at improving the preservability of the end products. The impact of various solvents and temperatures on the extraction yield is known through scientific literature, including British patent specification 1 526 553, among others. In certain methods, such as the one described in the U.S. Pat. No. 4,211,801, an organic solvent has been used as a medium to separate bran and endosperm fractions from each other.
The separation of oat gum is described in several processes, as in the method disclosed in U.S. Pat. No. 4,028,468, as well as in other scientific literature, being accomplished by extracting into an aqueous or alcalic solution and by precipitating with the aid of aliphatic alcohol or ammonium sulphate. In some processes, like the one disclosed in U.S. Pat. No. 4,435,429, the gum material is allowed to be hydrolyzed in order to reduce the viscosity, and is not recovered.
The antioxidative effects of oats are known from research publications. Phenolic compounds, like caffeic and pherulic acid derivatives, are considered major antioxidative factors, however some other oil components, tocopherols, among others, also have a synergetic effect. Nevertheless, this phenomenon has not been technically exploited. In certain processes, such as the one disclosed in the British patent specification 1 526 553 and U.S. Pat. No. 4,211,801, hydrogen peroxide is used to clarify the oil, and this procedure can be considered to bring about the inactivation of antioxidative factors possibly present. It is likewise known that many other fatty vegetable grains contain polyphenol compounds that have an antioxidative effect. The limited solubility into fats of these compounds has prevented their technical exploitation.
The methods for oat fractioning disclosed in patent literature so far rarely present the final fraction yield, which is one of the most essential criteria when evaluating the profitability of the process. The exact composition of the final fractions is rarely expressed, and most seldom is there given information about the physical or other properties of the end products, which would allow one to deduce properties of the fraction significant for industrial use, such as the viscosity and the molecular weight with regard to the vegetable gum fraction, the purity or residual protein content of the starch fraction and the proportions of various lipid fractions in the fat fraction. In the cited methods, the concentration of a component to a certain fraction is usually achieved, but not the degree of concentration or purity prerequisited by the technical use of the fraction. Major known oat fractioning processes are disclosed in the introductory portion of the specification of U.S. Pat. No. 4,435,429. As far as is known, none of them has resulted in a permanent technical application.